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I understand ailerons, elevators and rudders can be controlled to a very fine degree, and in precise flight, like formation flying, they can be used for very fine course adjustments to maintain the relative distance from another wingman.

But the throttle lever can regulate the thrust in range from near zero to several hundred kilonewtons by pushing it maybe 15cm forward. There's very little fine control to it and especially jet engines are sluggish to react to the changes.

How do pilots precisely fine-tune relative speed when traveling at high airspeed then? Are they using other tools - flaps, airbrakes maybe? Or am I underestimating the precision of the throttle, or missing some other mechanisms?

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The key in holding the same speed as your wingman or the other aircraft is not to find the "perfect" throttle position, the key is to slightly adjust the throttle.

When you look at cockpit-videos of those formation pilots (like this - move the camera to the throttle, it's a 360-degree video), you can see that they are constantly moving the throttle. They almost never stick the throttle at one position. In that way, they can slightly adjust the speed and stay in formation with the wingman for a long time.

While flying in close formation at high speed, it's the same. Little adjustments of the throttle helps the pilot to keep the same speed as the wingman-aircraft. Flaps are not used in high-speed-flying because they can only operate below a maximum speed, otherwise they could get damaged. By using the air-brake, the handling of the aircraft changes, therefore the air-brake is not used very often while flying in formation.

tl;dr:

Skill

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    $\begingroup$ So the short answer is skill? $\endgroup$
    – Holloway
    Dec 7, 2015 at 11:51
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    $\begingroup$ @Hollowy Yes, it's a combination of experience, feel for speed, training and many other things. All those together are 'skill'. $\endgroup$
    – jklingler
    Dec 7, 2015 at 11:52
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    $\begingroup$ If you think about it, it's very similar to how you can hold a precise position against another car on the motorway if you wanted to - you are continually adjusting the speed using the accelerator. You maybe don't know how much you do it - it ends up being second nature. $\endgroup$
    – Rory Alsop
    Dec 7, 2015 at 12:39
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    $\begingroup$ @RoryAlsop: The difference is that at 100km/h, if you match your speed to 1%, you're moving 1km/h relative to the other car, which is a crawl Plus the only other thing to match is your yaw. If you do that at 1000km/h you need a 10x as high precision, while you match pitch, yaw and roll simultaneously. $\endgroup$
    – SF.
    Dec 7, 2015 at 13:02
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    $\begingroup$ Still, consider consequences of an error. A gentle bump in F1 isn't disastrous. OTOH I remember stories about WW2 pilots, who, after running out of ammo, would flip V1 missiles with wing tips... $\endgroup$
    – SF.
    Dec 7, 2015 at 18:42
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You can match speed and fly formation with another aircraft much in the same way that you can match speed and drive in tight proximity to another automobile on the freeway; just a stream of minute and precise inputs to the accelerator, steering wheel and brake pedal. Aircraft have the additional challenge in that they move in three dimensions and their relative motions are much more inertial than an automobile; you cannot simply stop or arrest a relative closure as fast as you can in a car or truck.

Formation flying is an art form rarely practiced outside of the military because it is otherwise superfluous and useless in civilian aviation. Training begins with two ship formations at 75-100 feet apart and gradually reduces to 15 or so feet as the student pilot builds ability and confidence in the maneuver. Advanced formation flying or aerial refueling takes the student within 6-8 ft of another aircraft. By this point, maintaining formation has become second nature but the student still has to refine the precision to the point that he/she can hold on the boom or hook up with the drogue basket.

Formation flying starts with a process of the wingman 'walking up' on the lead with a closing speed which gradually reduces the closer the wingman gets to the lead ship. In general this is about 10kts for ever NM the two ships are separated by. Once the pilot assumes formation, it's a matter of keeping your eyeballs glued on the leader and making minute stick and throttle inputs. It just takes practice but you can get the hang of it within about 10-15 hours of practice formation flying.

There are limits to just how close you can fly next to another aircraft. Precision flying teams such as the USAF Thunderbirds or the USN Blue Angels will never fly closer than a 36 inch separation between aircraft. In addition this minimum spacing grows depending on the complexity and difficulty of the maneuvers which they are flying.

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  • $\begingroup$ Saw an inaccuracy in this post. The Blue Angels fly 18 inches wingtip-to-canopy separation. Talk about precision! $\endgroup$
    – Bassinator
    Oct 5, 2018 at 2:41

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